The present invention relates to an SOI device and a method for manufacturing the same, and more particularly, to an SOI device that can increase a charge storage capacity and improve the operation characteristics of transistors and a method for manufacturing the same.
As semiconductor devices become more highly integrated, operate at higher speeds, and lower power consumption, a semiconductor device (hereinafter referred to as an “SOI device”) using an SOI (silicon-on-insulator) substrate in place of a substrate formed of bulk silicon has been pursued in the art. This is because a device formed on the SOI substrate provides numerous advantages over a device formed on the bulk silicon substrate since it is possible to obtain high-speed operation due to a small junction capacitance, voltage reduction due to a low threshold voltage, and prevention of a latch-up phenomenon due to complete isolation.
A conventional SOI device includes an SOI substrate structure in which a buried oxide layer and a silicon layer are sequentially stacked on a silicon substrate, gates formed on the silicon layer of the SOI substrate, and junction regions formed in the silicon layer on both sides of the gates. Accordingly, the bodies of the SOI device are floated due to the presence of the junction regions and the buried oxide layer because the junction regions are formed such that the lower ends thereof contact the buried oxide layer.
Therefore, the SOI device has an FBC (floating body cell) structure in which the bodies are floated due to the presence of the junction regions and the buried oxide layer. In the SOI device having the FBC structure, it is not necessary to form capacitors and the size of cells can be decreased since charges can be stored in the floated bodies.
However, in the conventional SOI device, as the size of cells decreases to accommodate more highly integrated semiconductor devices, the volume of the bodies must also decrease, which causes the charge storage capacity of the bodies to degrade.
Additionally, in the conventional SOI device, the junction regions should be formed sufficiently deep to come into contact with the buried oxide layer in order to form the floated bodies. In this regard, a high dose ion implantation should be implemented to form the junction regions sufficiently deep. This causes the volume of the junction regions to increase. Consequently, a punch-through phenomenon is likely to occur between the junction regions that results in the deterioration of the operation characteristics of transistors.